Macro-channel water-cooled heat-sink for diode-laser bars

ABSTRACT

A water-cooled heat-sink for a diode-laser bar includes a copper-cooling-unit having an integral mount thereon for the diode-laser bar. The copper-cooling-unit is attached to a steel base-unit. The base-unit and the cooling-unit are cooperatively configured such that at least one cooling-channel is formed in the cooling-unit by the attachment of the base-unit to the cooling-unit. The cooling-channel is positioned to cool the mount when cooling-water flows through the cooling-channel.

TECHNICAL FIELD OF THE INVENTION

The present invention relates in general to diode-laser bar packaging.The invention relates in particular to packaging diode-laser bars on awater-cooled heat-sink.

DISCUSSION OF BACKGROUND ART

The term “packaging” applied to diode-laser bars refers to mounting adiode-laser bar, or an array of diode-laser bars, on some sort ofcooling-base or heat-sink. This base may be a relatively massive baseproviding a “conductively cooled package” (CCP). For higher poweroperation, the base is typically water-cooled, for example by amicro-channel arrangement.

A diode-laser bar includes a plurality of semiconductor layersepitaxially grown on a single-crystal substrate, with a plurality ofdiode-laser emitters defined in the epitaxial layers. Typically, thesubstrate is an n-type substrate, and layers are grown such that layersforming the “p-side” (anode-side) of the diodes are uppermost. Thediode-laser bar is soldered “p-side down” either directly onto theheat-sink or via a sub-mount having a coefficient of thermal expansion(CTE) intermediate that of the substrate material and the heat-sinkmaterial, which is usually copper.

Electrical connection to the diode-laser bars places the heat-sink andcooling-water therein, in electrical contract with the diode-laser barenergizing circuit. In an array of diode-laser bars, the water canshort-circuit electric connection to the bars, unless the electricalconductivity of the water is low. A common solution to this is to usede-ionized (DI) or high-resistance water. However, DI water is morecorrosive on metals than water from conventional building supplies, andthe use of DI water is expensive and inconvenient by comparison.

In micro-channel cooled arrangements, cooling-channels generally haveinternal dimensions of about 0.5 millimeters (mm) or less with waterforced through the channels by high pressure at relatively highvelocities. This also can lead to rapid corrosion of the copper in whichthe water cooling-channels are formed. This corrosion can be somewhatmitigated by plating the water cooling-channels with a metal such asgold. However, since the micro-channels are “internal” to the heat-sinkthe plating can only be achieved by immersion-plating usually usingforced-flow plating-solutions. This results in uneven plating, with theinternal nature of the channels preventing non-destructive inspectionfor quality assurance. There is a need for an improved water-cooledheat-sink for diode-laser bars, that will facilitate, or eliminate aneed for, plating of cooling-channels, and that does not require the useof de-ionized water.

SUMMARY OF THE INVENTION

The present invention is directed to methods and apparatus for coolingone or more diode-laser bars during operation. In one aspect,diode-laser apparatus in accordance with the present invention comprisesan electrically insulating ceramic sub-mount having a high thermalconductivity and first and second opposite sides. A diode-laser bar issolder-bonded to the first side of the ceramic sub-mount. A heat-sinkassembly for the diode-laser bar includes a base-unit and a coppercooling-unit, each thereof having first and second opposite sides. Thecooling-unit and the base-unit are attached together with the first sideof the base-unit mating with the second side of the cooling-unit. Thecopper cooling-unit has an integral mounting-member on the first sidethereof. The second side of the ceramic sub-mount is solder-bonded tothe mounting-member. The base-unit and the cooling-unit arecooperatively configured such that at least one cooling-channel havingfirst and second opposite ends is formed in the cooling-unit by theattachment of the base-unit to the cooling-unit. The cooling-channel isarranged to cool the integral mounting-member when cooling-water flowstherethrough. The base-unit includes an input-passage for directingwater into the first end of the cooling-channel and an output-passagefor conducting water away from the second end of the cooling-channel.

In one preferred embodiment of the invention, the apparatus is formounting a single diode-laser on a single mounting-member in the form ofa platform on the cool-unit. The cooling-channel is one of a pluralityof channels formed under the platform. The diode-laser bar emits in adirection parallel to the platform.

In another preferred embodiment of the invention, the apparatus is formounting a plurality of diode-lasers on a corresponding plurality ofmounting-members spaced apart and parallel to each other extendingupwards from the cooling-unit. The cooling-channel is one of a pluralityof cooling-channels with one thereof in each of the mounting-members.The diode-laser bars emit in a direction parallel to theextension-direction of the mounting-members.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, schematically illustrate a preferredembodiment of the present invention, and together with the generaldescription given above and the detailed description of the preferredembodiment given below, serve to explain principles of the presentinvention.

FIG. 1 is a three dimensional view that schematically illustrates awater-cooled heat-sink for a diode-laser bar stack in accordance withthe present invention including a copper cooling-unit having an integralarray of cooling-members, spaced apart and parallel to each other, withthe cooling-unit attached to a steel base with conduits for introducingcooling-water into and out of the heat-sink.

FIG. 1A is an exploded view from above of the heat-sink of FIG. 1schematically illustrating an integral manifold arrangement in the steelbase cooperative with the conduits of FIG. 1, and cooperative with anintegral array of fins cooperative with the array of cooling-members inthe copper cooling-unit for flowing water through the cooling-members.

FIG. 1B is an exploded view from below of the heat-sink of FIG. 1schematically illustrating a plurality of slots extending into thecooling-members of the cooling-unit, the slots being equal in number andspacing to the number and spacing of the cooling-members.

FIG. 1C is a cross-section view seen generally in the direction 1C-1C ofFIG. 1, schematically depicting a longitudinal aspect of a coolingmacro-channel formed by insertion of a fin of the base of FIG. 1A in aslot of the cooling-unit of FIG. 1B.

FIG. 1D is a cross-section view seen generally in the direction 1D-1D ofFIG. 1C schematically depicting a lateral aspect of the cooling-memberof the cooling-unit, macro-channels therein, and a diode-laser barbonded between two ceramic sub-mounts between adjacent ones of thesub-members, with one of the sub-mounts bonded to one of the adjacentones of the cooling-members.

FIG. 2 is a fragmentary plan view from above of the cooling-unit of FIG.1 schematically illustrating three diode-laser bars mounted betweenceramic sub-mounts, mounted in-turn between cooling-members of thecooling-unit, with the diode-laser bars connected electrically inseries.

FIG. 3 is a three-dimensional view, schematically illustrating apreferred embodiment of a water-cooled heat-sink in accordance with thepresent invention for a diode-laser bar, the heat-sink including acopper cooling-unit on which the diode-laser bar is mounted, the coppercooling-unit being attached to a steel base with conduits forintroducing cooling-water into and out of the heat-sink, with the baseand cooling-unit being configured such that, when assembled together, aplurality of spaced-apart parallel macro-channels if formed throughwhich water flows for cooling the cooling-unit.

FIG. 3A is an enlarged three-dimensional view schematically illustratingdetails of the cooling-unit of FIG. 3 including the diode-laser barsandwiched between ceramic (insulating) sub-mounts in the mannerdepicted in FIG. 2.

FIG. 3B is an exploded enlarged three-dimensional view schematicallyillustrating further details of the cooling-unit of FIG. 3 includingcomponents for isolating cooling-water from electrical connections tothe diode-laser bar.

FIG. 3C is a three-dimensional view from below illustrating a recessformed in the cooling-unit of FIG. 3, the recess including spaced apartgrooves which form the macro-cooling-channels when the cooling-unit isassembled on the base.

FIG. 3D is an enlarged three-dimensional view of the base of theheat-sink of FIG. 3 schematically illustrating a mating-block whichinserts into the cooling-unit recess of FIG. 3C for closing the groovesto form the macro-channels, and illustrating a system of plenums andconduits for leading water to and from the macro-channels.

FIG. 3E is a hypothetical three-dimensional view of the system ofconduits, plenums, and macro-channels of FIG. 3D, with surrounding partsof the base and cooling-unit removed to reveal details of the system.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, wherein like components are designated bylike reference numerals, FIG. 1 schematically illustrates a water-cooledheat-sink 20 for a diode-laser bar stack in accordance with the presentinvention. Heat-sink 20 includes a copper cooling-unit 22 includingelongated rectangular cooling-members (mounting-members) 24 spaced apartand parallel to each other, extending upward from the cooling-unit in awidth-direction of the cooling-members, as illustrated. Diode-laserbars, not shown in this view, are mounted between the cooling-members.Preferably, the cooling-members 24 are an integral part of cooling-unit22, i.e., the cooling-unit including the cooling-members is machinedfrom a single piece of copper. Cooling-unit 22 is attached by screws 26to a base 28 including conduits 30 for introducing cooling-water intoand out of the heat-sink. The choice of which conduit is an inputconduit and which conduit is an output conduit, here, is somewhatarbitrary. Base 28 is preferably made from a material which is easilymachined. One preferred material is stainless steel.

In operation of heat-sink 20, cooling-water flows into base 28 through aselected one of conduits 30, through each of cooling-members 24 (inparallel) in cooling-unit 22 and out of the other conduit 30. Adescription of a preferred arrangement for this cooling-water flow isset forth below with reference to FIG. 1A, FIG. 1B, and FIG. 1C.Fittings or coupling units for connecting to conduits 30 to supply waterand disposal hoses or tubes are not shown for simplicity ofillustration. Such fittings can be selected from several well-known andcommercially available fittings.

FIG. 1A is an exploded view from above of heat-sink 20 of FIG. 1schematically illustrating an integral manifold arrangement 31 in thebase 28 cooperative with conduits 30, and cooperative withcooling-members 24 in cooling-unit 22. Manifold 31 includes elongatedplenums 36 machined into surface 32 of base 28. Here, the input plenumis designated as plenum 36A and the output plenum is designated asplenum 36B, corresponding to the designation of the input and outputconduits with which the plenums connect. Screws 26 for attaching unit 22to base 28 are not shown in this view. The screws extend through holes27, here countersunk, in unit 22, and are received by threaded holes 29in base 28.

Between plenums 36A and 36B is an array of boat-shaped fins 34 (finswith quarter-rounded ends). The fins are spaced apart and parallel toeach other with a center-to-center spacing equal to the center-to-centerspacing of cooling-members 24 in unit 22. Surrounding the manifoldarrangement of plenums and fins is a trench or groove 40 configured foraccommodating a water-seal (not shown in this view) such as an elastomerring or the like. It is preferable that the base, including plenums,fins, and the water-seal groove are machined from a single piece ofmaterial.

FIG. 1B is an exploded view from below schematically depicting slots 42extending into cooling-members 24 of cooling-unit 22. Also depicted arethreaded holes 46 in base 28. These are provided for attaching theheat-sink unit to a base, walls, or a support structure of a housing inwhich the inventive heat-sink will be used.

FIG. 1C is a cross-section view seen generally in the direction 1C-1C ofFIG. 1. This view depicts a longitudinal aspect of slots 42 in unit 22.Here, the slots have a bathtub-like longitudinal shape, cooperative withthe boat-shape of fins 34 such that, when each fin is inserted into acorresponding slot, a macro-channel 50, having a height H, is formed ineach cooling-member 24. Height H, of course results from a difference inthe depth of the slot and the height of the fin being less than thedepth of the slot).

Macro-channel 50 has rounded corners resulting from the longitudinalshape selection of the fins and slots. The ends of channel 50 align withplenums 36A and 36B in base 28. The plenums are in fluid communicationwith conduits 30 via ducts 46A and 46B in base 28. FIG. 1D is across-section view seen generally in the direction 1D-1D of FIG. 1Cschematically depicting a lateral aspect of cooling-members 24 ofcooling-unit 22 with macro-channels 50 having a width W.

A particular advantage of this inventive, two-piece construction forproviding cooling macro-channels 50 is that surfaces that form thechannels can be plated, for example gold-plated, by conventionalelectroplating methods. The plating can be inspected before heat-sink 22is assembled. Preferably, at least those surfaces provided by coppercooling-unit 22 should be plated. Surfaces of the channels provided bybase 28 may be plated if the selected base material is not inherentlycorrosion resistant.

Regarding dimensions of macro-channels 50, for a cooling-member 24having a width of about 1.0 mm, each macro-channel preferably has aheight H of between about 3.7 mm and about 4.0 mm, and a width W ofabout 0.5 mm. These dimensions are provided for guidance only and shouldnot be considered limiting.

The shape of the rounded corners of the macro-channels is not critical,but is provided to ensure that there is free flow of cooling-water asdepicted, avoiding any sharp corners or recesses in which water could betrapped. Suitable channel-dimensions and corner-shape can be readilydetermined, by trial and error, for any predetermined range of pressuredifference between inlet and outlet, using commercially availablethermal-analysis software such as SolidWorks, from Dassault Systèmes ofVélizy-Villacoublay, France. The channel-width should bringcooling-water close enough to the surface of the cooling-members tooptimize cooling while still leaving the cooling-member sufficientlyrigid to support bonding operations for diode-laser bars.

Continuing with reference to FIG. 1D, a lateral aspect of a particularlypreferred mounting scheme in accordance with the present invention for adiode-laser bar in a space 25 between adjacent cooling-members 24 isdepicted. Here, a diode-laser bar 60 is solder-bonded between metallizedsurfaces 64A and 64B of two ceramic (insulating) sub-mounts 62A and 62B.The ceramic material of the sub-mounts is preferably relatively highlythermally conductive.

Another factor influencing the choice of ceramic material is the CTE,which should be compatible with substrate material of the diode-laserbar, the solder used for the bonding and the diode-laser bar substratematerial. For gallium arsenide (GaAs) substrates, suitable ceramicmaterials include beryllium oxide (BeO) and aluminum nitride (AlN).

These materials permit that a hard solder such as gold/tin (Au/Sn)solder can be used to bond the diode-laser bar to the sub-mount withoutinducing intolerable stress on the diode-laser bar due to thermalcycling (on and off operation) during normal use. One advantage ofbonding the diode-laser bar between two ceramic sub-mounts is thatwhatever stress is produced is balanced, thereby minimizing distortionof the diode-laser bar and alignment of emitters thereof. Slow axismisalignment of emitters in a diode-laser bar is whimsically termed“smile” by practitioners of the art.

One of the sub-mounts, between which diode-laser bar 60 is bonded, has ametallized surface 66 solder-bonded to one of the cooling-members. InFIG. 1D sub-mount 62A is bonded to the cooling-member. Preferably athermally conductive packing 68, such as a shim or plated soldermaterial, is inserted between the “un-bonded” sub-mount (here, sub-mount62B) and the cooling-member to put the sub-mount in thermalcommunication with a cooling-member. Clearly, a better thermalcommunication is established between the bonded sub-mount and thecooling-member to which it is bonded. Accordingly, it is preferable thatthe epitaxial-layers side (p-side or anode-side) of the diode-layer baris bonded to the “bonded sub-mount”. However, with a sufficiently thinsub-mount, for example less than about 0.4 mm thick, and the inclusionof shim 68, there is still effective cooling of the n-side of theepitaxial layers of the diode-laser bar.

FIG. 2 is a fragmentary plan view from above of the cooling-unit of FIG.1 schematically illustrating three diode-laser bars mounted betweenceramic sub-mounts mounted in-turn between cooling-members of thecooling-unit as discussed above with reference to FIG. 1D. It should benoted in particular that the cooling-members are sufficiently long thatthe entire length of a diode-laser bar can be in communication with thestraight portion (between rounded corners) of the cooling-channels inthe cooling-members.

Further, ceramic sub-mounts 62A and 62B are sufficiently long to permita partial overlap of a length equal to or greater than the length of thediode-laser bar. The partial overlapping is done with the non-overlappedportions of the sub-mounts at opposite ends of the diode-laser bar, andin this instance, the overlapping is sequentially alternated betweenadjacent pairs of sub-mounts.

This alternate partial overlapping arrangement of the metallizedsub-mounts permits convenient connection of the diode-laser bars inseries. In this arrangement, reading from left to right, a positive(Pos) lead is connected to the non-overlapped part of sub-mount 62A atone end of diode-laser bar 60 and a negative (Neg) lead is connected tothe non-overlapped part of sub-mount 62B at the other end of thediode-laser bar. The negative lead from sub-mount 62A is connected to apositive lead attached to sub-mount 62A of the next-diode-laser bar, andso on.

The connecting leads (sheet or strip electrodes) are made sufficientlyrigid that the shape of the electrodes is retained in normal use, andcannot accidentally come into contact with an exposed part of acooling-member. Because of this, and because of there being anelectrically insulating sub-mount on each side of the diode-laser bars,cooling-water in the heat-sink is electrically isolated from thediode-laser bars.

For convenience of illustration, optical axes (well-known fast- andslow-axes) of the diode-laser bars are shown inset in FIG. 2. Theemission direction of the emitters of the diode-laser bars is asindicated, i.e., perpendicular to the plane of the drawing, in theextension-direction of the cooling members. A plurality of diode-laserbars arranged in this manner is typically referred to as avertical-stack or fast-axis stack of diode-laser bars.

Exemplary dimensions in the arrangement of FIG. 2 are as follows. Thelength of cooling-members 24 is about 20 mm; the thickness of thecooling-members is about 1 mm; the width (“thickness”) of spaces 25between the cooling-members is about 1 mm. Here again, these dimensionsare provided for guidance only, and should not be considered as limitingthe present invention.

Principles of the invention described above in the context of cooling afast-axis stack of diode-laser bars are equally applicable to cooling asingle diode-laser bar. By way of example, FIG. 3 schematicallyillustrates a preferred embodiment of a diode-laser bar package 70including water-cooled heat-sink in accordance with the presentinvention. The diode-laser bar is in a “sandwich” 90 between metallized,ceramic, electrically insulating sub-mounts as described above for theinventive fast-axis stack arrangement. The diode-laser bar axes areshown inset in FIG. 3. The heat-sink of package 70 includes a coppercooling-unit 72 on which the diode-laser bar sandwich is mounted. Thecopper cooling-unit is attached to a steel base 74 with a conduit 76 forintroducing water into the package and a conduit 77 for delivering waterfrom the package. Details of the conduit arrangements (not shown) withinbase 74 and cooling-channels or macro-channels (also not shown) arediscussed in detail further hereinbelow.

Continuing with reference to FIG. 3, and with reference in addition toFIG. 3A, and FIG. 3B, diode-laser bar sandwich 90, comprisingdiode-laser bar 60 bonded between ceramic sub-mounts 62A and 62B isbonded to cooling-unit in the form of an integral mounting-platform 73of cooling-unit 72. The emission direction of the diode-laser bar isparallel to surface 73A of the mounting platform.

The diode-laser bar is bonded epitaxial-side (p-side or anode-side) downon sub-mount 62A, which is the sub-mount in contact with platform 73. Aseparate cathode-side cooling-block (cooling-unit) 80 is bonded toceramic sub-mount 62B. A thermally conductive packing or shim 92 ofsolder material, such as indium (In) or the like, places cathode-sidecooling-block in thermal communication with a raised portion 75 of thecooling-unit (see FIG. 3A). Extended end-portions 80A (see FIG. 3B) ofthe cathode-side cooling-block are provided for mounting collimatingoptics (not shown) for the diode-laser bar. Cooling-water flows incontact with platform 73 and part of raised portion 75 as outlined inphantom in FIG. 3B. Terminal blocks 82 and 84 (anode and cathoderespectively) are attached to raised portion 75 of cooling-unit byscrews and insulating bushings (not shown), with insulating pads 86placed between the blocks and the raised portion of the cooling-unit.This is important in preventing any electrical contract between theterminal blocks and the cooling-unit.

Electrical contact with the diode-laser is made from electrical leadsclamped at one end thereof between terminal blocks 82 and 84 andcorresponding insulators 86, and bonded the opposite end thereof to the(metallized) diode-laser sides of ceramic sub-mounts 62A and 62B. InFIG. 3A, a cathode lead is depicted symbolically as a wire-lead 94. Inpractice, this is a sheet electrode (for current carrying capacity) butis not depicted as such in FIG. 3A to avoid obscuring other details ofthe heat-sink-assembly. In FIG. 3B, examples 87A and 87B of suchsheet-electrodes are depicted. Dashed lines indicate the connection ofelectrodes 87A and 87B to sub-mounts 62A and 62B, respectively. Hereagain, this method of electrical connection to the diode-laser bymetallized sides of the ceramic sub-mounts is for avoiding anyelectrical contact between the diode-laser bar and the heat-sink.

Details of cooling-arrangements for the inventive heat-sink are nextdescribed with reference to FIG. 3C, FIG. 3D and FIG. 3E. FIG. 3C is athree-dimensional view from below illustrating a recess 96 formed incooling-unit 72. The recess includes spaced-apart grooves 98 which formmacro-cooling-channels when cooling-unit 72 is assembled onto the baseof the heat-sink. Ridges 100 separate grooves 98 (except for end ones98′ thereof). The grooves terminate in raised (less deep) portions 102at each end of the groves (only one visible in FIG. 3C).

Regarding exemplary dimensions in FIG. 3C, the grooves (between portions102) are preferably about 0.6 mm deep (as defined by the height or depthdifference between the grooves and ridges 100). The grooves arepreferably about 1.2 mm wide. The length of recess 96 including thegrooves is preferably long enough to extend along most of the length ofplatform 73 of cooling-unit 72, and wide enough to extend partiallyunder raised portion 75 of the cooling-unit, as can be seen in thephantom outline in FIG. 3B. The total depth of recess 96 (at the groves)is preferably selected such that grooves 98 are within about 0.3 mm ofthe surface of platform 73 (see FIG. 3B) of the cooling-unit.

FIG. 3D is an enlarged three-dimensional view of the base 74 of theinventive heat-sink. A footprint of cooling-unit 72 is depicted inphantom. Water conduits within the base are also depicted in phantom.Continuing reference is made to FIG. 3C.

Base 74, here, is assumed to be machined from a single piece of metalsuch as stainless-steel. A mating-block portion 104 of the base isconfigured to engage raised portions 100 in recess 96 of FIG. 3C forclosing grooves 98 to form macro-channels. In that regard, mating-block104 is a close fit in the length of the recess and a close fit betweenraised portions 102 in the recess. On opposite sides of block 104 aremachined elongated plenums 106A and 106 B. The block and plenums aresurrounded by a machined groove 108 for accommodation a sealing ring.

Plenums correspond in position to raised (channel-terminating) portions102 in recess 96 of FIG. 3C. Plenum 106A is in fluid communication witha straight portion 76A of inlet conduit 76. Plenum 106B is in fluidcommunication with a straight portion 77A of outlet conduit 77. Theselection of conduit 76 for inlet, and conduit 77 for outlet, issomewhat arbitrary, and should not be considered as limiting the presentinvention.

FIG. 3E is a hypothetical three-dimensional view of the system (100) ofconduits, plenums, and grooves of FIGS. 3C and 3D, with surroundingparts of the base and cooling-unit removed to reveal details of thesystem. Here it can be seen that the engagement of block 104 (in thebase) of FIG. 3D with the recess (in the cooling-unit) of FIG. 3C, whenthe base and cooling-unit are assembled together, causes the grooves tobecome macro-channels (macro-conduits) 102, which link inlet and outletplenums 106A and 106B, respectively, and corresponding inlet and outletconduits 76 and 77 respectively. Flow though the macro-channels is asindicated.

The present invention is described above in terms of two embodiments. Inone aspect of the invention a heat-sink includes a single-piece coppercooling-unit, and a single-piece base-unit, which, when assembledtogether, form macro-channels in the cooling-unit through which watercan be circulated. The term “macro-channel” as used herein implies thatthe channel preferably has a minimum dimension not less than about 0.2mm.

One embodiment of the inventive heat-sink is configured for mounting afast-axis stack of diode-laser bars. The other is configured formounting a single diode-laser bar, however, a slow-axis (horizontal)array of bars could utilize a plurality of these heat-sinks on a commonplatform. In either embodiment, the two-piece construction allowscorrosion-resistant plating of the copper portions of the macro-channelsbefore the heat-sink is assembled.

In another aspect of the invention, a diode-bar is solder-bonded betweenan overlapping region of two metallized, ceramic sub-mounts before beingmounted on the cooling-unit of the heat-sink. Each of the ceramicsub-mounts is in thermal communication with the cooling-unit for coolingthe diode-laser bar. Electrical connection is made to non-overlappingportions of the metallized ceramic sub-mounts for making electricalconnection to the diode-laser bar. This arrangement has an advantagethat the diode-laser bar, and electrical connections thereto, areelectrically isolated from the cooling-unit and the cooling-watertherein, for resisting corrosion of macro-channels in the cooling-unitby the water.

The arrangement also has an advantage that stresses induced in thediode-laser bar due to CTE mismatch between the material of thediode-laser bar and the ceramic are balanced out, minimizing slow-axismisalignment of emitters in the diode-laser bar and providing forincreased reliability under temperature cycling. This latter advantagecan be enjoyed even with heat-sink arrangements that are notwater-cooled, i.e., passively or conductively cooled.

The present invention is not limited to the above-described embodiments.Rather the invention is limited only by the claims appended hereto.

What is claimed is:
 1. Diode-laser apparatus, comprising: anelectrically insulating, ceramic sub-mount having a high thermalconductivity and first and second opposite sides; a diode-laser barsolder-bonded to the first side of the ceramic sub-mount; a heat-sinkassembly including a base-unit and a copper cooling-unit, each thereofhaving first and second opposite sides, the cooling-unit and thebase-unit being attached together with the first side of the base-unitmating with the second side of the cooling-unit the copper cooling-unithaving an integral mounting-member on the first side thereof, the secondside of the ceramic sub-mount being solder-bonded to themounting-member; the base-unit and the cooling-unit being cooperativelyconfigured such that at least one cooling-channel having first andsecond opposite ends is formed in the cooling-unit by the attachment ofthe base-unit to the cooling-unit, with the cooling-channel arranged tocool the integral mounting-member when cooling-water flows therethrough;and the base-unit including an input-passage for directing water intothe first end of the cooling-channel and an output-passage forconducting water away from the second end of the cooling-channel.
 2. Theapparatus of claim 1, wherein there is a single water-seal between thebase-unit and the cooling-unit.
 3. The apparatus of claim 2, wherein thewater seal includes a generally rectangular groove formed in thefirst-side of the base-unit and elastomer ring compressed in the grooveby the attachment of the first-side of the base-unit to the second sideof the cooling-unit.
 4. The apparatus of claim 1, wherein the base-unitis formed from stainless steel.
 5. The apparatus of claim 1 wherein theintegral mounting-member is an elongated rectangular member having alength and a width and extending in the width-direction thereof from thefirst side of the cooling-unit, and wherein the cooling-channel isformed within the mounting member.
 6. The apparatus of claim 5, whereinthe cooling-channel is formed from an elongated slot having a depth anda first length formed in the second side of the cooling-unit andextending into the mounting-member, and an integral extension on thefirst side of the base-unit having height less than the depth of theslot, and a second length less than the first length, and extendingpartially into the slot leaving an open portion at each end thereof toprovide the input and output ends of the cooling-channel.
 7. Theapparatus of claim 6, wherein the mounting-member is one of a pluralityof such mounting-members spaced apart and parallel to each other eachthereof having a cooling-channel therein having first and second endsformed by one of a corresponding plurality of slots in the cooling-unitand extensions on the base-unit.
 8. The apparatus of claim 7, whereinthe slots are plated with gold before the base-unit is attached to thecooling-unit.
 9. The apparatus of claim 7, wherein the cooling-waterinput-passage includes an elongated input-plenum and elongatedoutput-plenum in the base-unit, the input plenum in fluid communicationwith the first ends of the cooling-channels in the mounting-members, theoutput-plenum in fluid communication with the second ends of thecooling-channels in the mounting-members, the cooling-waterinput-passage further including an input-conduit in fluid communicationwith the input-plenum and the cooling-water output-passage furtherincluding an output-conduit in fluid communication with the outputplenum.
 10. The apparatus of claim 9, wherein the base-unit is formedfrom stainless steel.
 11. The apparatus of claim 5, wherein thediode-laser bar has an emission-direction parallel to theextension-direction of the mounting-member.
 12. The apparatus of claim1, wherein the mounting-member is platform formed on the first side ofthe cooling-unit and having a mounting-surface to which the ceramicsub-mount is solder-bonded, the diode-laser bar having anemission-direction parallel to the mounting-surface of the platform. 13.The apparatus of claim 12 wherein the cooling-channel is one of aplurality of cooling-channels formed in the cooling-unit under theplatform.
 14. The apparatus of claim 13, wherein the plurality ofcooling-channels is formed from a rectangular recess in the second sideof the cooling-unit, the recess having a plurality of elongated groovesin the base thereof spaced apart and parallel to each other withadjacent ones thereof separated by ridges, and an integral rectangularextension-block on the first side of the base-unit, the extension-blockextending into the recess, engaging the ridges and partially coveringthe grooves such that the grooves become the cooling-channels, theextension-block being configured relative to the recess to leave each ofthe grooves uncovered at first and second opposite ends thereof forproviding the first and second ends of the cooling-channels.
 15. Theapparatus of claim 14, wherein the grooves in the recess are plated withgold before the base-unit is attached to the cooling-unit.
 16. Theapparatus of claim 14, wherein the cooling-water input-passage includesan elongated input-plenum adjacent in the base-unit on one-side of theextension-block and an elongated output-plenum in the base-unit on anopposite side of the extension block, the input-plenum in fluidcommunication with the first ends of the cooling-channels, theoutput-plenum in fluid communication with the second ends of thecooling-channels, the cooling-water input-passage further including aninput-conduit in fluid communication with the input-plenum, and thecooling-water output-passage further including an output-conduit influid communication with the output plenum.
 17. Diode-laser apparatus,comprising: a plurality of diode-laser assemblies, each thereofincluding an electrically insulating, ceramic sub-mount having a highthermal conductivity, and first and second opposite sides, and includinga diode-laser bar solder-bonded to the first side of the ceramicsub-mount; a heat-sink assembly including a base-unit and a coppercooling-unit, each thereof having first and second opposite sides, thecooling-unit and the base-unit being attached together with the firstside of the base-unit mating with the second side of the cooling-unit;the copper cooling-unit having a plurality of integral elongatedrectangular mounting-members extending from the first side of thecooling-unit the mounting-members being spaced apart and parallel toeach other, and each diode-laser bar assembly being bonded to acorresponding one of the mounting-members and emission direction of thediode-laser bar parallel to the extension direction of themounting-members; a plurality of cooling-channels, one formed in each ofthe mounting-members, and each thereof having opposite first and secondends, each of the cooling-channels being formed from an elongated slothaving a depth and a first length formed in the second side of thecooling-unit and extending into a corresponding one of themounting-members, and an integral extension on the first side of thebase-unit having height less than the depth of the slot, and a secondlength less than the first length, and extending partially into the slotleaving an open portion at each end thereof providing the input andoutput ends of the cooling-channel; and the base-unit including aninput-passage for directing water into the first ends of thecooling-channels and an output-passage for conducting water away fromthe second ends of the cooling-channel.
 18. The apparatus of claim 17,wherein the cooling-water input-passage includes an elongatedinput-plenum and elongated output-plenum in the base-unit, the inputplenum in fluid communication with the first ends of thecooling-channels in the mounting-members, the output-plenum in fluidcommunication with the second ends of the cooling-channels in themounting-members, the cooling-water input-passage further including aninput-conduit in fluid communication with the input-plenum and thecooling-water output-passage further including an output-conduit influid communication with the output-plenum.